I confess that it's been 50 years since I took shop classes in college and while I've done some things regularly since then both professionally and as part of my hobby work, I've had very limited experience in certain areas. SO ...
I've got a bar of aluminum that I had to drill and tap several 1/4-20 holes in. The bar is roughly 7"x1"x1.25" and drilling and tapping the holes through the thickness (1") was a good refresher course, but the hole through the height (1.25") has me stumped. Without thinking it through, I drilled the hole and started tapping. But the tap's cutting length is only 1" and the shaft behind it is too thick to pass though previously tapped metal.
A Google search reveals that there are some custom taps that are made for extra long holes but for a one-off I don't need a custom tap. I think I found that there are some types where the shaft is narrow enough to pass through the previously tapped hole to allow deeper holes to be done, but the nomenclature is confusing.
I need help and I'd love to learn the right terminology. As a start, to get the project back on track, I'd really appreciate it if someone could tell me, perhaps, the name and part number at ENCO for the right tap for my hole. As a follow-up, perhaps a link or three to pages which explain the differences would also be greatly appreciated.